1. Technical Field
The present invention relates to a two-stage rotary compressor, and more specifically relates to a two-stage rotary compressor having features in a structure for supplying a rotary compressing element with oil and in a gas seal structure in a muffling chamber provided in relation to the rotary compressing element.
2. Related Art
A two-stage rotary compressor including a motor-drive element in a closed vessel and a rotary compressing element driven by this motor-drive element has been known. For example, a two-stage rotary compressor shown in FIG. 5 will be described. In FIG. 5, an upper portion in a closed vessel A is provided with a motor-drive element B composed of a stator and a rotor, the rotor is attached to an upper end portion of a rotating shaft C, a lower portion in the closed vessel A is provided with a rotary compressing element G composed of a low stage side rotary compressing element E and a high stage side rotary compressing element F through a partition plate D, and supporting members H and I are attached to upper and lower portions of the rotary compressing element G respectively. Each of the low stage side rotary compressing element E and the high stage side rotary compressing element F includes a disc-shaped cylinder J and a roller K, which rotates on the inside of the cylinder eccentrically. These rollers K are fitted on eccentric portions L provided on the rotating shaft C respectively. Further, a low pressure chamber and a high pressure chamber are respectively formed in the cylinders J by the fact that a vane biased with a spring not shown always abuts on an outer circumferential surface of the roller K. The upper and lower supporting members H and I are provided with bearing portions M and N at the center portions respectively, and support the rotating shaft C. Muffling chambers P and Q are respectively provided so as to surround outer circumferences of the bearing portions M and N, and cover plates R and S for closing the opening surfaces of the muffling chambers P and Q are respectively attached.
When a low pressure refrigerant gas is introduced through a lead-in pipe T connected to the closed vessel, this low pressure refrigerant gas is sucked into a suction port in the lower supporting member I and sucked from this suction port to the low pressure chamber in the cylinder J of the low stage side rotary compressing element E where the refrigerant gas is compressed to an intermediate pressure by eccentric rotation of the roller K. The refrigerant gas compressed to the intermediate pressure is discharged from the high pressure chamber of the cylinder J to the muffling chamber Q in the lower supporting member I, and further it passes through a passage (not shown) communicating with the muffling chamber Q to be discharged into the closed vessel A. The intermediate pressure refrigerant gas discharged into the closed vessel A is then taken out of a discharge opening Z of the closed vessel A to the outside and cooled. After that the refrigerant gas is sucked into a suction port provided in the upper supporting member H from a return lead-in pipe U, and is sucked into the low pressure chamber in the cylinder J of the high stage side rotary compressing element F, where it is compressed to high pressure by eccentric rotation of the roller K. This refrigerant gas compressed to the high pressure is discharged from the high pressure chamber to a muffling chamber P in the upper supporting member H and is discharged from a discharge port communicating with the muffling chamber P to the outside of the closed vessel A through a lead-out pipe V connected to the closed vessel A.
Then the high pressure refrigerant gas discharged to the outside of the closed vessel A is supplied to for example a gas cooler in a refrigeration cycle in an air conditioner or the like, and after cooling the refrigerant gas by the gas cooler, it is pressure-reduced by an expansion valve and vaporized by an evaporator. Then the refrigerant gas passes through an accumulator to be returned from the lead-in pipe T to the compressor. The thus formed two-stage rotary compressors have been disclosed in for example Japanese Laid-Open Patent Publications No. 2003-97479 and No. H02-294587 etc.
In the conventional two-stage rotary compressors, two problems to be solved are pointed out. The first problem in these problems to be solved is with a structure of supplying a rotary compressing element with oil.
In the conventional two-stage rotary compressor, a bottom portion in the closed vessel A forms an oil reservoir, oil is pumped up from the oil reservoir with an oil pump W attached to a lower end portion of the rotating shaft C to be raised along the inner surface of a hole provided along the axial direction of the rotating shaft C, and then the oil is oozed out of small holes provided at appropriate portions of the rotating shaft C to an outer surface of the rotating shaft to lubricate bearing portions M and N in the upper and lower supporting members H and I and rotating portions of the low stage side compressing element E and high stage side compressing element F so that sliding portions are lubricated. To be liable to ooze the oil from the small holes of the rotating shaft C upon the lubrication, a vent hole X, which communicates with the outer circumferential surface of the partition plate D through the inner hole (rotating shaft C is penetrated therethrough) formed in the partition plate D, is provided.
Further, as shown in FIG. 5, the partition plate D is provided with an oil supply hole Y, which communicates the vent hole X with a passage (which connects the suction port formed in the upper supporting member H to an inlet of the low pressure chamber in the cylinder J) formed in the cylinder J in the high stage side rotary compressing element F, so that a part of oil contained in gas, which passes through the vent hole X, is supplied to a passage side of the cylinder J. The oil supplied to the passage side of the cylinder J flows into the low pressure chamber together with refrigerant gas, which passes through this passage, and lubricates the sliding portion of the roller K, which rotates eccentrically along the inner circumferential surface of the inside of the cylinder.
However, since the partition plate D is formed thinly in its plate thickness and the oil supply hole Y is provided on a portion of the vent hole X having a thinner plate thickness, the length of the oil supply hole Y cannot be lengthened and a diameter of the oil supply hole Y cannot be increased. Accordingly, an amount of oil supplied to the inside of the cylinder J in the high stage side rotary compressing element F becomes excessive. If the amount of supply oil is excessive (amount of oil more than needed), the performance of lubrication is lowered and a discharge amount of oil becomes excessive by an increased in input due to oil compression or the like.
In the low stage side rotary compressing element E, a low-pressure refrigerant gas is introduced through the lead-in pipe T. Although oil in the refrigerant gas is separated by an accumulator before this lead-in of the refrigerant gas, a considerable amount of oil is still contained in the refrigerant gas. Thus, the low pressure refrigerant gas containing a large amount of oil is introduced into a suction port of the lower supporting member I through the lead-in pipe T, and the refrigerant gas is sucked into a low pressure chamber of the cylinder J through a passage formed in the cylinder J of the low stage side rotary compressing element E. Thus an appropriate amount of oil is supplied to the inside of the cylinder J of the low stage side rotary compressing element E. Further, oil on the inner diameter side of the roller is supplied from a gap between the end surfaces of the rollers.
In the present invention it is intended to solve the first problem of the above-mentioned prior art, or to specifically provide a two stage rotary compressor, which can supply a necessary amount of oil into a cylinder of a high stage side rotary compressing element.
The second problem of problems to be solved in conventional two stage rotary compressors is a gas seal structure of a muffling chamber provided in connection with a rotary compressing element.
Although the conventional two stage rotary compressor supports the rotating shaft C on the upper supporting member H and the lower supporting member I, the upper supporting member H is positioned near the motor-drive element B and supports the vicinity of an upper end portion of the rotating shaft C, which journals a rotor of the motor-drive element B. Thus a load imposed on a bearing portion M becomes larger than a load imposed on the lower supporting member I, which supports a lower end portion of the rotating shaft C. Therefore, the bearing portion M of the upper supporting member H is formed longer than the bearing portion N of the lower supporting member I and is reinforced by fitting a bushing X0 inside the bearing portion M.
Since high pressure refrigerant gas compressed by the high stage side rotary compressing element F is discharged into a muffling chamber P in the upper supporting member H, high accuracy seal properties are required so that no leak is caused between an opening surface of the muffling chamber P and a cover plate R, which closes the opening. Accordingly, between an outer circumference of the bearing portion M in the upper supporting member H and an inner circumferential surface of the center hole in the cover plate R is attached an O ring W0 and in a connection portion between the upper supporting member H and the cover plate R is interposed a gasket Y0. Further, in a case where the upper supporting member H is formed of a ferrous sintered material, in order to improve gas seal properties it is necessary to apply cutting work to an upper end surface of the upper supporting member H to improve the flatness whereby the degree of adhesion to the gasket Y0 is increased.
When the O ring W0 is attached, the outer circumferential surface of the bearing portion M in the upper supporting member H is subjected to a concave grooving work. However, since the wall thickness of the bearing portion M is formed thinly, there are problems that the concave grooving work is troublesome and the working cost is increased. When the wall thickness of the bearing portion M is formed thick a muffling chamber P provided around the outer circumference of the bearing portion M becomes narrow and sufficient space cannot be ensured. Thus, the wall thickness of the bearing portion M must be formed thinly. Although the inner circumferential surface of the center hole in the cover plate P can be subjected to concave grooving work, the concave grooving work is also troublesome, which leads to an increase in working cost.
In the present invention it is intended to solve the conventional second problem or to eliminate the concave grooving work for O ring attachment in the outer circumference of the bearing portion in the upper supporting member and the cutting work in the upper supporting member.